A method for the testing of detonators



Patented Jan; 25, 1927.

uurrso STATES 11.615.6 6 PATENT OFFICEQQ norms. wonnnn, or DARMSTADT, GERMAN A METHOD FOR HE TESTING or nnronaro ifis No Drawing. Application filed April 8, 1925, Serial lVo."21,722.aiid -in GermanyJu iie 16, 1 924 For the determination of the priming action of detonating caps there has hitherto served almost universally the detonation thereof on a lead plate about 3 to 6 millimetres in thickness, which rests upon a pierced cast iron support hollow 1n the mid dle, so that when the priming'efiiectof the detonating cap, which is held b'y-a curved guard, is sufficient, the'lcad plate is penetrated. The size of the penetration, the marginal rim 'orburr thereof in the upper and being distinguished comparatively, but cssentially only as to'whether the detonating cap is usable at'all and has not become un usable owing to. moisture .for instance or other prejudicialactions, in which case the penetration is unusually defective or fails entirely, and instead of theradial streaking, only rather coarse dividing of the sleeve metal owing to insufficient detonation of .the detonating cap is recognizable on the lead plate.

Above all however it has been found that owing to a whole series of more external influences the penetration of the lead plate admits of being essentially modified without the actual priming action being thereby affected, so any comparison of this action is unreliable. Thus by forcing in dumplings or so-called mandrelling unusually large lead-plate penetrations are obtained, without a clear increase in the priming action being connected therewith.

The true priming action of the detonating caps has therefore hitherto been tested-by detonating a series of explosives of different degrees of sensitiveness in the usual cartridges of about 100 grammes each by means of the detonating cap in question, and from the more or less complete detonation of the explosive a conclusion has been come to as regards the priming action of the detonator. Here again the decision is more of a qualita: tive nature. Above all, however, the method is costly and can only be adopted on shootground ing s usual lead-plate method could be Now the tive contents.

so transformed that it still remains a'labora'tory met rod, hardly-involves auy=. -greater expenditure, and receives strongly quantita- But if one fills a few'grammes of the explosive with regard to which the priming action of the detonator is to be tested intoa. second mctal slceve or casing only'a little" lnore roomy than the detonating cap itself,

and then sets the latter in the explosive of the former and this in turn on the lead plate of the usual shooting apparatus for detonating caps, the detonatiug of the cap a'd mits as hitherto of being brought about with the fuse, and with it the detonating ofthe explosive in the outer casing. After the shot the lead plateshows, according to whetherit in the larger sleevewasprimed by the deto-e nating cap or not. If the priming effect of the detonating cap was insufficiently strong, or the explosive too insensitive, the lead plate is not penetrated, and shows either no impression at all, or only inconsidcrable damaging of the surface by the metallic fragments of the explosive casing.

N 'w if one takes as an explosive a homogeneous substance, such as trinitrotoluol for example, and phlegznatizes it, for the grading of its insensitiveness,with paraffin oil for example of definite quality in increasing quantities, one obtains as itwere a series of explosives ofaccurately graded increasing insensitiveness, in which there are two successive stages, one of which is detonated by the detonating cap to be tested, the lead plate being penetrated, and the second of which, the less sensitive stagemore phlcgmatizedis not detonated at all oronly incompletely, so that the lead plate is no longer penetrated. The priming action of the detonator to be tested 'is therefore characterized by the two well defined stages of phlegmatized explosive, which express the action numerically within the methodical limits 'as rarrowly and therefore as accurately as is desired.

Example.

In a drawn copper sleeve, or casing of a length of millimetres, 8.5 millimetres in diameterandliaving a wall thickness of 0.15 of a milliflnbtre at the top, 0.25 of a millimetre close to the bottom, and a bottom thickness of 0.85 of a millimetre, is placed two grammes of phlegmatized explosive. It

is penetrated or not, whether the explosive lit) ' is produced by intimately mixing. in the mortar 50 grammes of pure trinitrotoluol with from 2 to per cent, according to the insensitiveness desired--in stages of per cent each-01? paraflin' oil, (specific gravity at 18.5 centigrade- 0.89, viscosity at 15.5:31.1 degrees Engler) with the aid of to 40 cubic centimetres of distilled ether free from water and residues, which must evaporate again after the kneading t030 to 40,after' which rubbing three times thronghwire gauze of 144 meshes per square centimetre makes the product completely homogeneous. Under a ram of the shape of the detonating-cap to be inserted it is pressed with a pro-sure of 100 kilogrammes per square centimetre. The finished detonating cap, provided with a fuse is now inserted in the space left for it inthe explosive in the larger casing, and by a suitable devicet\vo or three small Wooden wedges--- held in this position. and thus detonate-d out-he lead plate in the usual detonatortesting apparatus. The pres ram, the dimensions of which for the sake of saving space. must correspond to the size of the detonating cap to he tested, should preferably he so constructed that the upper surfaces of the explosive and detonator charges are at the same level so that a number of-difi'e'rcnt.

rams are required according to the usual standard sizes of detonators. If the diameter of the outer explosivecasing is selected, as described. only a little more roomy than that of the detonator casing No. 8, it is then ensured that the height -of the detonator bottom above the height of the layer of exp osive is almost completely equal in the case of the detonator sizes 3 to 8.'and only a little different in the case of No. 10.

The results obtained are in complete agreement in the case of one and the same kind and strength of detonating cap, and

show for example that by mandrelling or employing dumplings in the pressing of the detonating caps their true priming efi'ect according to the method described above. is not influenced at all or is only influenced to an immaterial extent. 7

Having now particularly described and ascertained the nature of my saidinventionand in what manner the same is to be performed, I declare that what I claim is 1. A process for the quantitative meas- I .uring of the priming action of detonating employing a ram for compressing the explosive to form acavity therein.

3. A process for the quantitative measuring of the priming action of detonating caps as claimed in claim 1, wherein the cavity is of such a depth that the surfaces of the explosive and detonator charges are of the same levelafter the insertion of the detonator in the explosive.

AJA process for the quantitative measuring of the priming action of'detonating capsas claimed in claim 1 consisting in ,em-

ploying small wooden we gas and inserting.

the wedges between the detonator and the side of the holder for maintaining the deto-- nator in the desired position.

In testimony whereof I have signed my name to this specification.

DR. 'LOTHAR WOBLER. 

